The invention relates to a method of reducing oxide-containing fine-particle ores, wherein the oxide-containing ore particles are melted and reduced in a rotationally symmetric melting vessel in the presence of solid, liquid or gaseous carbon carriers by the action of a plasma jet of a plasma burner, as well as to an arrangement for carrying out the method.
From Austrain Pat. No. 257,964 a method of reducing metallic oxides by means of an electric arc plasma is known. The electric arc plasma contains a hydrocarbon gas, which serves as a reduction gas. The plasma arc is struck between a plasma burner, vertically arranged in the cover, and a bottom electrode arranged in the bottom of a melting vessel. The metal melt forming is covered by a slag layer. The reduction of the metal oxides takes place in the slag layer. The carbon and/or hydrogen must be prevented from contacting the molten metal bath, since otherwise there exists the danger that carbon will become dissolved, resulting in an undesirable carbon increase. Furthermore, there would be the risk of hydrogen diffusing into the metal melt.
This known method has the disadvantage that the thermal energy dissipating from the electric arc plasma constitutes a big load on the refractory lining of the melting vessel, since the strongest heat radiation occurs perpendicular to the axis of the plasma jet. On account of this fact, the service life of the lining of the melting vessel is relatively short. Furthermore, a sufficiently thick slag layer always must be maintained, since the reduction has to take place in the slag layer and in its surface, respectively. Reduction gases must not reach the metal bath.
From the published European application No. 0,037,809-Al a method for producing molten pig iron is known, according to which prereduced oxide-containing raw-material particles are top-charged into a fluidized bed, formed by carbon particles and an oxygen-containing carrier gas, through the cover of the melting vessel. As they travel through the same, the particles are heated, completely reduced and melted, additional energy being supplied to the fluidized bed by an additional firing that is designed as a plasma heating. With this known method it is necessary to use a strongly prereduced ore (prereduced to approximately 60 to 80%). In the melting vessel, thus prereduced ore merely is subjected to an afterreduction.
The invention has as its object to provide a method, and an arrangement for carrying out the method, which makes possible to get from the ore to the molten metal in one single step and in one single melting vessel. In particular, metals having low carbon contents are to be attained. Furthermore, the melting vessel, in particular its brickwork, is to have a long service life despite high energy loads, and the energy supplied is to be optimally utilized.